In the last 33 years, Carolyn Porco has had a hand in some of NASA's highest profile missions. She was an integral part of the Voyager imaging team, then the public face for the Cassini mission. Now, she and her colleagues are now laying the groundwork for a mission to Enceladus, with the goal of finding life.

"We have reasons now to believe that our very best chances of finding extraterrestrial life in our lifetimes – and almost certainly, if it is there at all, a second genesis of life – is the ocean of Enceladus," Porco said in an email interview with Popular Mechanics.

"It is why there are those of us who want NASA to return there as soon as possible with the kind of instrumentation that could say for sure, one way or another, if life has gotten started there. It could turn out to be as dead as a doornail, but at Enceladus we have the chance to answer this question now. So what are we waiting for?"

The origins of the potentially revelatory mission go back quite a way. In 2005, Cassini confirmed that Saturn's tiny moon had geyser activity. There had been inklings before, especially during the Voyager mission, but Cassini was able to actually find real evidence of an undersea ocean that could be habitable. It's a possible birthplace for life, kept liquid by the moon's daily tidal distortion, caused by its eccentric orbit and its changing distance from Saturn.

"We knew for decades of Enceladus' spatial coincidence with the huge, diffuse, donut-shaped ring of tiny smoke-sized icy particles known as the E ring," Porco says. "And of course Voyager found it was a moon that showed the effects of internal activity. Very surprising for such a small moon. So, soon after the Voyager Saturn flybys were over, it was proposed that there might be geysers of water erupting from the surface, creating that E ring."

"There's nothing in this world like being the first to discover some fundamental fact of nature."

Porco became part of the Voyager mission during the Saturn flybys in 1980 and 81. As a graduate student at CalTech, she'd already studied the interaction between Saturn's rings and the moons nearby. "There were so many new findings that the Voyager imaging team couldn't keep up with it all." She wound up working many of them into her dissertation.

By the time that Voyager 2 flew by Uranus in 1986, Porco was brought on to the Voyager team full time, tasked with studying the planet's newly discovered ring system. She continued on to similar work with Neptune, revealing the relationships between planets and their rings and moons in unprecedented detail.

By the early 1990s, she found, along with fellow researcher Mark Marley (now at Ames Research Center in California), that internal oscillations within Saturn can give rise to certain features of the planet's ring system without requiring interactions with orbiting moons. It was an unknown phenomena at the time, but a finding that was ultimately confirmed by Cassini.

"There's nothing in this world like being the first to discover some fundamental fact of nature," she said. "It's profoundly satisfying."

When Cassini was finally given the green light as a NASA mission, Porco was named the imaging lead. But space is big, and despite a launch in 1997 Cassini didn't arrive near its destination until 2004. In the meantime, Porco took on the challenge of engineering a lunar burial.

Eugene Shoemaker—an astronomer who focused much of his work on asteroids and the early chronology of the solar system— would have been an Apollo astronaut, but was sidelined by Addison's disease which left him earthbound. Porco helped make sure that, after Shoemaker died in 1997, he got to go to the moon after all.

"Gene went on to do many important things in the study of the solar system, but this Apollo story was legend in my business," she said. "So, when I learned that he had died–which was impossibly sad for those of us who idolized him–and that his body was to be cremated, the first thought that came to my mind was, 'Let's send him to the Moon!'" His ashes were carried to the moon on the Lunar Propector mission, along with an epigraph designed and created by Porco.

Porco has strong opinions on the future of the space program. NASA is no stranger to changing priorities. As administration's change, so do the agency's goals, handed down from on high. It's not a situation Porco is particularly fond of . "[It's] not the way to run a space program." And while she's cautiously optimistic of private space companies, she has her doubts. "I am uneasy about having scientific exploration depend on profit-making companies."

"To me, there will always be need for governments to support the largest, most daring and most scientifically significant projects," she says. "So, the best possible future requires both enterprises."

There's a lot of evidence to suggest that Enceladus is not that different from what we know here on Earth

But those are big, sweeping changes and in the near term, there's the matter of NASA's scientific exploration goals. Of course she wants the Enceladus mission and a proposal is currently being drafted up, with the hopes that it can gain the same kind of traction as the Europa mission. Both, after all, are a quest for life in our own backyard, not to mention there's a lot of evidence to suggest that Enceladus is not that different from what we know here on Earth.

"We have found evidence for hydrothermal activity of the type that powers the Lost City hydrothermal region and its biota on the floor of the Atlantic," she says. "We also know Enceladus' ocean has a salinity comparable to the Earth's oceans, and an alkalinity that is consistent with hydrothermal activity."

In a pinch (or as a bonus), she'd also love to see a mission to Neptune, "a fascinating planet very unlike Jupiter and Saturn. Neptune has been neglected since 1989. It deserves a mission that is Cassini in scope, and it's time we return," she says.

But whatever the specifics of her next project, each new mission is the culmination of decades worth of fascination and hard work.

"I was drawn to astronomy by a teenage existential quest," she says. "Around 13, I was deep into wondering about the meaning of life, and what I was doing here. I turned to religion, but that did nothing for me."

"I got to wondering where was here. So, I began studying astronomy and became enthralled by what I learned. By the time I finished high school, I knew I wanted to become an astronomer. By the time I finished college, I knew I wanted to be part of the American space program. And that's exactly what I did."

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